From the experimental found that the viscosity of c-PGA aqueous solution declined steadily as CaCl2 solution added gradually, at CaCl2 final concentration 0.01–0.05%. So, effects of CaCl2 addition on flask culture of B.subtilis CGMCC2108 were studied, including viscosity of culture broth, yield, the number of viable cells, and molecular
weight of c-PGA.